Octave from QT: undefined reference - c++

Question

I would like to run Octave script from Qt GUI application.
Here is .pro file:
...
win32 {
INCLUDEPATH += c:/Octave/Octave-4.2.1/include/octave-4.2.1/octave
LIBS += c:/Octave/Octave-4.2.1/lib/octave/4.2.1/liboctave.dll.a \
c:/Octave/Octave-4.2.1/lib/octave/4.2.1/liboctinterp.dll.a
DEPENDPATH += c:/Octave/Octave-4.2.1/bin
}
...
Here is .cpp file (example is taken from docs):
#include <iostream>
#include <octave/oct.h>
#include <octave/octave.h>
#include <octave/parse.h>
#include <octave/interpreter.h>
int
main (void)
{
string_vector argv (2);
argv(0) = "embedded";
argv(1) = "-q";
octave_main (2, argv.c_str_vec (), 1);
octave_idx_type n = 2;
octave_value_list in;
for (octave_idx_type i = 0; i < n; i++)
in(i) = octave_value (5 * (i + 2));
octave_value_list out = feval ("gcd", in, 1);
if (out.length () > 0)
std::cout << "GCD of ["
<< in(0).int_value ()
<< ", "
<< in(1).int_value ()
<< "] is " << out(0).int_value ()
<< std::endl;
else
std::cout << "invalid\n";
clean_up_and_exit (0);
}
When I am trying to compile C++ code from Qt Creator I have the following error:
undefined reference to feval(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, octave_value_list const&, int)
I also have the following errors from compiler:
undefined reference to Array<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::nil_rep()
undefined reference to Array<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::resize_fill_value() const
undefined reference to Array<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::resize_fill_value() const
but when I Ctrl+Click on Array or feval - Qt Creator opens the appropriate files.
I can also compile the example c++ file using the following command from Octave GUI:
mkoctfile --link-stand-alone embedded.cc -o embedded
What library/path should I add?
Thank you very much in advance.

Answer 1

If you run mkoctfile on your example from above (I copied it into main.cc) with verbose, you'll see all flags needed:
mkoctfile -v --link-stand-alone main.cc
g++ -std=gnu++11 -c -fPIC -I/usr/local/include/octave-4.2.0/octave/.. -I/usr/local/include/octave-4.2.0/octave -I/usr/local/include -pthread -fopenmp -g -O2 main.cc -o main.o
g++ -std=gnu++11 -I/usr/local/include/octave-4.2.0/octave/.. -I/usr/local/include/octave-4.2.0/octave -I/usr/local/include -pthread -fopenmp -g -O2 -rdynamic -fPIC main.o -L/usr/local/lib/octave/4.2.0 -L/usr/local/lib -loctinterp -loctave
Now you have to add these to your QtCreator. (I guess -std=gnu++11 is missing)

Answer 2

It seems from the error that gcd function does not exist, or it cannot find reference to it. I don't know about gcd function whether it is part of octave or it is your custom defined, but surely it's missing a reference to it.